The present invention relates to a copier, facsimile machine, printer or similar image forming apparatus of the type forming a toner image on a sheet or similar toner image carrier. More particularly, the present invention is concerned with a method which allows the toner image carrier to be repetitively used without deforming it by removing only a toner from the carrier, and a toner applicable thereto.
A copier, for example, has been implemented by various image forming processes in the past, e.g., a diazo process and a silver halide process. Today, an electrophotographic copier capable of forming images on plain paper sheets, i.e., plain paper copier (PPC) is predominant over the others. In parallel with the remarkable growth of information-oriented society, technologies for producing a great amount of copies at high speed and producing high quality copies have been developed. Further, peripheral equipment are available which are easy to operate and can readily produce a great amount of copies. While such a situation allows many persons to share the same information through the copies, new informations are generated at all times, copied, and discarded. The result is the consumption of a huge amount of papers.
To prevent environmental disruption ascribable to lumbering, a current trend is toward the use of papers regenerated from used papers, instead of papers made from wood pulp. However, the problem with such regenerated sheets is that a large scale facility is needed to remove ink from the copies and other used papers. In the light of this, there has been developed toners having particular compositions which render dyes transparent when illuminated by near infrared rays (880 nm). With such toners, it is possible to use papers a number of times. Specifically, Japanese Patent Laid-Open Publication No. 100728/1976 discloses a method which removes an image from a copy by use of toluene, tetrachloroethylene or similar solvent. Japanese Patent Laid-Open Publication No. 137266/1989 teaches mixing an absorptive high molecule gel with a toner containing at least a binding resin and a coloring agent. The toner with the absorptive high molecule gel is expected to remove a toner fixed on an OHP (OverHead Projector) sheet or similar resinous film by a PPC, so that the film may be repetitively used.
However, the method using a toner having a particular composition as stated above is not practicable without resorting to a bulky device and great energy for the radiation of near infrared rays. Moreover, since stoners having particular compositions available at the present stage of development are only blue toners, they cannot provide images with sufficient contrast and are expensive.